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The detection of noncatastrophic faults in conjunction with other factors can be used to determine the remaining life of an electric drive. As the frequency and severity of these faults increase, the working life of the drive decreases, leading to eventual failure. In this paper, four methods to identify developing electrical faults are presented and compared. They are based on the short-time Fourier transform, undecimated-wavelet analysis, and Wigner and Choi--Williams distributions of the field-oriented currents in permanent-magnet ac drives. The different fault types are classified using the linear-discriminant classifier and k-means classification. The comparison between the different methods is based on the number of correct classifications and Fisher's discriminant ratio. Multiple-class discrimination analysis is also introduced to remove redundant information and minimize storage requirements. Index Terms--Choi--Williams, intermittent fault detection, multiple discrimination analysis (MDA), permanent-magnet ac (PMAC) drives, short-time Fourier transform (STFT), undecimated discrete wavelet transform (UDWT), Wigner distribution.

The detection of noncatastrophic faults in conjunction with other factors can be used to determine the remaining life of an electric drive. As the frequency and severity of these faults increase, the working life of the drive decreases, leading to eventual failure. In this paper, methods are presented to identify developing electrical and mechanical faults based on both the short-time Fourier transform and wavelet analysis of the field-oriented currents in permanent-magnet ac drives. The different fault types are classified by developing a linear discriminant classifier based on the transform coefficients. Index Terms--Intermittent fault detection, permanent-magnet ac (PMAC) drives, short-time Fourier transform (STFT), undecimated discrete wavelet transform (UDWT).

Pole-phase modulation adjusts the pole-phase ratio of an induction machine and requires a multileg, multiphase inverter. This paper analyzes an n-leg, n-phase inverter, and presents techniques for n-phase space vector pulse width modulation (SVPWM). In particular, nine-phase SVPWM is developed and implemented on a nine winding induction machine. The nine-phase SVPWM is compared to nine phase sine-triangle PWM in terms of dc bus utilization. Index Terms--Inverter, pole phase modulation, space vector pulse width modulation.

A nonlinear robust output feedback control is designed for a sixth-order model of an induction motor. The control uses only measurement of the rotor position and stator currents. It contains two observers, a second-order observer to estimate the rotor flux from the stator current and a third-order high-gain observer to estimate the rotor speed and acceleration from its position. The control is robust to uncertainties in the rotor and stator resistances, and a bounded time-varying load torque. It guarantees that the speed tracking error can be made arbitrarily small by choice of certain design parameters. Moreover, when the speed reference and load torque are constant, it ensures asymptotic regulation. Simulation results agree well with the analysis.